The present invention relates to an optical retrieving system.
When information stored in a film (for example, a microfilm) is retrieved by an optical retrieving system comprising a light source and a lens assembly for receiving light from the light source, it is a great convenience to simultaneously shift or move both of the light source and the lens in the same direction by the same amount to extend the range of possible retrieval. However, in this case, it is very difficult to maintain an accurate optical alignment between the light source and the lens during the movement thereof; misalignment often results in inaccurate retrieval. Another drawback arising from the movement of the lens is that it is necessary for an operator to perform the frequent focusing of the lens with respect to an output portion (for example, an projector) of the optical retrieving system.